On Fri, 6 Sep 2013 10:52:38 -0700
"Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
> > What exactly does "extended quiescent state" mean? (Note, that's a
> > rhetorical question)
>
> In which case my rhetorical (and therefore useless) answer has to be
> "it is a quiescent state that is extended". ;-)
>
> Sorry, couldn't resist...
Of course you couldn't ;)
>
> > I wonder if we should change "rcu_cpu_ignore()" for "rcu_eqs_enter()"
> > and "rcu_cpu_heed()" for "rcu_eqs_exit()", as IMHO that's much more
> > straight forward to understand than trying to wrap you head around what
> > a quiescent state is, and why we are entering it or exiting it.
> >
> > It also flat out explains to people that rcu is not processing that
> > current CPU, and things like rcu_read_lock() should not be used.
> >
> > Then we can say "rcu_cpu_is_ignored()" for things like
> > "rcu_is_cpu_eqs()".
>
> Currently, none of RCU's _eqs functions are exported, so they have
> the potential to confuse only people working on the RCU implementation
> itself, who had better understand what "eqs" means.
Yeah, that's what I thought, and never cared about the "eqs" meaning.
>
> But I do count your vote against "eqs" appearing in the name of any
> function exported by RCU.
Right, their shouldn't be any "eqs" functions that are global to users
outside of the RCU infrastructure.
>
> How about if I made rcu_is_cpu_idle() be as follows?
>
> int rcu_is_cpu_idle(void)
> {
> int ret;
>
> ret = (atomic_read(&per_cpu(rcu_dynticks.dynticks,
> raw_smp_processor_id())) & 0x1) == 0;
> return ret;
> }
>
> This should allow existing uses to function properly and should allow
> you to use it as well.
>
You already said it wont work, but I still would have been against
using it, because I wouldn't be checking if rcu thinks the CPU is idle,
as NO_HZ_FULL has nothing to do with idle.
-- Steve
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